Contemporary fluid dispense systems are well suited for dispensing precise amounts of fluid at precise positions on a substrate. A pump transports the fluid to a dispense tip, also referred to as a "pin" or "needle", which is positioned over the substrate by a micropositioner, thereby providing patterns of fluid on the substrate as needed. As an example application, fluid delivery systems can be utilized for depositing precise volumes of adhesives, for example, glue, resin, or paste, during a circuit board assembly process, in the form of dots for high-speed applications, or in the form of lines for providing underfill or encapsulation.
Contemporary dispensing pumps comprise a syringe, a feed tube, a dispense cartridge, and pump drive mechanism. The syringe contains fluid for dispensing, and has an opening at its distal end at which a feed tube is connected. The feed tube is a flexible, hollow tube for delivering the fluid to the cartridge. The cartridge is hollow and cylindrical and includes an inlet neck at which the opposite end of the feed tube is connected. The inlet neck directs the fluid into the hollow, central cartridge chamber.
A feed screw disposed longitudinally through the center of the cylindrical chamber transports the fluid in Archimedes principle fashion from the inlet to a dispensing needle attached to the chamber outlet. A continuously-running motor drives the feed screw via a rotary clutch, which is selectively actuated to engage the feed screw and thereby effect dispensing. A bellows linkage between the motor and cartridge allows for flexibility in system alignment.
Pump systems can be characterized generally as "fixed-z" or "floating-z" (floating-z is also referred to as "compliant-z". Fixed-z systems are adapted for applications that do not require contact between the dispense tip and the substrate during dispensing. In fixed-z applications, the dispense tip is positioned and suspended above the substrate by a predetermined amount, and the fluid is dropped onto the substrate from above. In floating-z applications, the tip is provided with a standoff, or "foot", designed to contact the substrate as fluid is delivered by the pump through the tip. Such floating-z systems allow for tip travel, relative to the pump body, such that the entire weight of the pump does not bear down on the substrate.
Pump manufacturers commonly include their own custom interface for mounting dispense needles to the pumps. Customers investing a great deal of resources in a particular pump system are therefore limited to purchasing compliant dispense needles directly from the pump manufacturers. This arrangement is not optimal for the customer, since after-market dispensing needles are often times superior in performance and reliability. For example, the dispense needles disclosed in U.S. patent application Ser. No. 09/491,615, filed Jan. 26, 2000, incorporated herein by reference, offer the capability of precise dispensing at higher throughput rates, higher reliability, and reduced dispensing widths. Such high-performance dispense needles are incompatible with the current aforementioned manufacturer-specific systems.